1. Field of the Invention
The present invention relates to a semiconductor device low temperature test apparatus, and more particularly to a low temperature test apparatus that prevents a drop in measurement quality resulting from the generation of frost, dispenses with the conventional thermostatic chamber to thereby miniaturize the apparatus, and shortens the turnaround time.
2. Description of the Related Art
A shipping test for a semiconductor integrated circuit device such as an LSI (referred to as an IC hereinbelow) includes a high temperature test step and a low temperature test step. Generally, the operation of the IC is ensured over a comparatively broad temperature range from a high temperature to a low temperature. Accordingly, a shipping test requires a high temperature test step of checking whether or not operation is normal in a high temperature atmosphere of 90° C., for example, and a low temperature test step of checking whether or not operation is normal in a low temperature atmosphere of −15° C., for example. Ordinarily, operational defects often occur in a high temperature atmosphere, however, for example, in the case of flash memory and the like, a drop in the power source level in a low temperature atmosphere sometimes leads to a defect such that programming operations cannot be performed normally. It is therefore necessary to perform a low temperature test in order to eliminate such a defect.
Disposed in a conventional shipping test line are: a high temperature test apparatus comprising a thermostatic chamber maintained in a high temperature atmosphere, and a low temperature test apparatus comprising a thermostatic chamber maintained in a low temperature atmosphere. A plurality of ICs undergoing testing, which are placed in a test tray, are introduced to the respective thermostatic chamber of the high temperature test apparatus and the low temperature test apparatus; the ICs undergoing testing are connected in turn to an internal socket, and predetermined operational tests are performed.
Where the high temperature test apparatus is concerned, the thermostatic chamber is provided with a heater, the test tray is introduced via the delivery door, and the tray is discharged via the discharge door. Similarly, with regard to the low temperature test apparatus, a liquid nitrogen bath is connected to the thermostatic chamber, and a low temperature atmosphere is produced by this liquid nitrogen.
A conventional low temperature test apparatus has a structure in which liquid nitrogen is employed to produce a low temperature atmosphere within the thermostatic chamber, and therefore temperature control of the IC undergoing testing takes time. In addition, the thermostatic chamber must also be provided with a constitution to pre-cool the IC undergoing testing before the IC undergoing testing is connected to a socket to perform the test, as well as a temperature recovery constitution for returning the IC undergoing testing to a normal temperature following the test. There is thus the problem of an increase in size of the test apparatus.
Further, in order to prevent the generation of frost in the thermostatic chamber, a baking process is required in the thermostatic chamber so as to eliminate moisture in the thermostatic chamber, before a low temperature state is established for the thermostatic chamber and after same has been restored to a normal temperature state. The waiting time required for the temperature drop which corresponds to the accompanying temperature rise induces a decrease in the throughput of the test apparatus.
Furthermore, even after performing this baking process within the thermostatic chamber, when, after the thermostatic chamber has dropped to a low temperature, testing is implemented continually over a long period, frost is generated in the sections of the connection terminals of the measurement IC socket in the thermostatic chamber, whereby a short circuit results between the connection terminals. In the test steps, at the time of a contact test to check for a connection defect between the IC undergoing testing and the measurement IC socket, and of a leak test to check for a short-circuiting defect between the terminals of the IC undergoing testing, a connection is confirmed, despite there being a connection defect, due to a short circuit caused by frost on the socket connection terminals, or a short circuit defect is detected even in the absence of a short circuit between the IC terminals, respectively, whereby the test quality is dropped.
In order to prevent the above problem, there is a requirement to periodically release the low temperature state of the thermostatic chamber and perform a baking process on the interior thereof, and such a periodic baking process also lowers the throughput of the test apparatus.
Conventionally, a low temperature test apparatus not equipped with a thermostatic chamber is disclosed by Japanese Patent Application Laid-open No. S53-50982. This low temperature test apparatus has a constitution that supplies a low temperature atmosphere generated by Peltier elements to an IC undergoing testing via a heat pipe and that performs cooling as a result of the heat pipe pressing against the top face of the IC undergoing testing. However, in this method, the IC undergoing testing is cooled indirectly by the Peltier elements and the IC undergoing testing cannot be cooled highly accurately or in a short time. In addition, the generation of frost on the connection terminals of the socket cannot be avoided.